S-(chlorophenyl) o,o-dialkyl phosphorodithioates



United States Patent ()1 S-(CI-ILOROPHENYL) 0,0-DIALKYL PHOSPHORO-DITHIOATES Harold R. Slag h, Midland, Mich, assignor to The Dow ChemicalCompany, Midland, Mich., a corporation of Delaware No Drawing.Application April 4, 1956 Serial No. 575,962

5 Claims. (Cl. 260-461) This invention is concerned with theS-(chlorophenyl) 0,0-dialkyl phosphorodithioates having the formula 7 so-x R s-i' 0 X In this and succeeding formulas, R represents achlorophenyl radical and X represents methyl or ethyl. These newcompounds are colorless or light yellow liquids, somewhat soluble inmany organic solvents and of very low solubility in water. They havebeen found to be active as parasiticides and are adapted to be employedas active toxic constituents of compositions for the control ofbacteria, mites and insect organisms such as the Mexican bean beetle andhouseflies.

IThe new compounds may be prepared by reacting an alkali metal methylateor alkali metal ethylate with an S-(chlorophenyl)phosphorodichloridodithioate of the formula. V

p is 01 R s l The reaction is carried out in an inert organic solventsuch as benzene, toluene, methylene dichloride or carbon tetrachlorideand conveniently in the alcohol employed in the preparation of thealcoholate. Good results are obtained when employing two molecularproportions of the alkali metal alcoholate with each molecularproportion of the phosphorodichloridodithioate reagent. In practice, thealcoholate employed is preferably the sodium salt and may be prepared byreacting the corresponding alcohol with sodium. The reaction between thealcoholate and the phosphorodichloridodithioate is somewhat exothermicand takes place smoothly at temperatures of from 10 to 60 C. Thetemperature may be controlled by regulating the rate of contacting thereactants as well as by external cooling. Upon completion of thereaction, the desired product may be separated in conventional fashion.

In carrying out the reaction, the alkali metal alcoholate is contactedportionwise with the phosphorodichloridodithioate reagent dissolved inthe reaction solvent. The latter operation is carried out with stirringand at a temperature of from -10 to 60 C. Upon completion of thereaction, the solvent may be removed by evaporation, the residuedissolved in a water-immiscible solvent such as methylene dichloride orbenzene and the solvent solution washed with water. The solvent is thenremoved by fractional distillation under reduced pressure to obtain thedesired product as a liquid residue.

In an alternative method, the new compounds may be prepared by reactingan alkali metal salt of a chlorobenzenethiol (alkali metal-SR) with an0,0-dialkyl phosphorochloridothioate having the formula 7 2,897,227Patented July 28, 1959 EXAMPLE 1 'S (4-chl0r0p'henyl) 0,0-dimethylphosphorodithioate OCH;

Sodium (3.31 grams, 0.144 mole) was dissolved in milliliters of methanolto preparea methanol solution of sodium 'methy-late. This solutionwasadded portionwise with stirring to 20 grams (0.072 mole) ofS-(4-chlorophenyl) phosphorodichloridodithioate dispersed in 25milliliters of methanol. The addition was carried out over a period of30 minutes and at a temperature of from 10 to 20 C. Stirring wasthereafter continued for one hour at room temperature to complete thereaction. The methanol was then removed by evaporation and the residuediluted with benzene and washed with water. The washed mixture wasthereafter fractionally distilled under reduced pressure to separate thebenzene and obtain an S-(4-chlorophenyl) 0,0-dimethyl phosphorodithioateproduct as a colorless liquid. This product has a specific gravity of1.3819 at 25 C. and a refractive index n/D of 1.6013 at 25 C. Y

- EXAMPLE 2 S-(qfrchlorophenyl) 0,0-diethyl phosphorodithioate v s 0cm.

Sodium (0.144 mole) was dissolved in 100 milliliters of ethanol toprepare an ethanol solution of sodium ethylate. This solution was addedportionwise with stirring to 0.072 mole of S-(4-chlorophenyl)phosphorodichloridodithioate dispersed in 25 milliliters of ethanol. Theaddition was carried out in 30 minutes and at a temperature of from 10to 20 C. After the addition, the mixture was stirred for one hour atroom temperature to complete the reaction. The reaction mixture was thenprocessed as described in Example 1 to obtain an S-(4-chlorop'henyl)0,0-diethyl phosphorodithioate product as a viscous liquid having aspecific gravity of 1.2455 at 25 C. and a refractive index n/D of 1.5697at 25 C.

EXAMPLE 3 S-(2,5-rlidhlo'rophenyl) 0,0-diethyl phosphorodithioate2,5-dichlorobenzenethiol (17.9 grams, 0.1 mole) and 2.3 grams (0.1 mole)of sodium was dissolved in milliliters of methanol to prepare a methanolsolution of the sodium salt of 2,5-dichlorobenzenethiol. This solutionwas added gradually with stirring to 18.85 grams (0.1 mole) of0,0-diethyl phosphorochloridothioate. The addition was carried out overa period of 20 minutes and at a temperature of from 25 to 33 C. Afterthe addition, the mixture was stirred at 35 to 38 C. for three hours tocomplete the reaction. The methanol was removed by evaporation and theresidue diluted with benzene and washed with water. solvent, there wasobtained an S-(2,5-dichlorophenyl) Upon evaporation of the p 0,0-diethylphosphorodithioate product as a light yellow liquid having a specificgravity of 1.3234 at 25 C. and a refractive index n/D of 1.5663 at 25 C.

2,4,5-triehlorobenzenethiol (21.35 grams, 0.1 mole) and-2.3 grams (0.1mole) of sodium was dissolved in 150 milliliters of methanol to preparea methanol solution of the sodium salt -,of 2,4,5-trichlorobenzenethiol.This solution 'was added portionwise .with stirring to 18.85 grams (0.1mole) of 0,0-diethyl phosphorochlo-ridothioate. The addition was carriedout-in 30 minutes andat a temperatureof from 5 to C. After the addition,the mixture was stirred and :heated at 30 to 35 C. for 1.5 hourstocomplete the reaction. The reaction mixture was then processed asdescribed in Example 3 to obtain an S-(2,4,5-trichlorophenyl)0,0-diethyl phosphorodithioate product as a viscous liquid having aspecific gravity of 1.3442 at 25C. and a refractive index n/ D of 15511at 25 C.

The -S-(-chloropl1enyl) phosphorodichloridodithioates employed asstarting materials may be prepared by reacting :a molecular excess ofphosphorus thiochloride (PSCl with a suitable chlorobenzenethiol in thepresence of anhydrous magnesium chloride as catalyst. Good results areobtained when employing from five to ten moles of phosphorusthiochloride per mole 'of the benzenethiol reagent. In carrying out thereaction, the reactants and catalyst are mixed together and warmed untilthe evolution of hydrogen chloride .of reaction is substantiallycomplete. The reaction mixture is then filtered to remove'the catalystand the filtrate fractionally distilled under reduced pressure toseparate the product.

The new S-(chlorophenyl) 0,0-dialkyl phosphorodithioates are efiectiveas parasiticides and are adapted to be employed for the controlof'household and agricultural pests. For such use the products may bedispersed on a finely divided carrier and employed as dusts. The newproducts may also be employed in oils, as constituents in wateremulsions or in Water dispersions. In a representative operation,percent vcontrols of houseflies and Mexican bean beetles have beenobtained with aqueous compositions containing 100 .parts :byweight .of5S-j(4- chlorophenyl) 0,0-diethyl .phosphorodithioate per mil lion partsby weight of aqueous composition. 1

I claim: v

1. An S-(chlorophenyl) 0,0-dialkyl 'phosphorodithioate having theformula V whereinRrepresents a .chlorophenyl radicalandX represents1 amember of the group consisting of methyl and ethy.

2. S-(4-chlorophenyl) -0,0-dimethyl phosphorodithioate. r

3. S-(4-chlorophenyl) 0,0-diethyl phosphorodithioate.

4. S-(2,5-d1chlorophenyl) Q,O-die thyl phosphorodithioate. i

5. S-. (2,4,5-trichlorophenyl) Q,'Odiethyl phosphorodithioate.

References Cited in the file of this patent UNITED .STATES PAIENTS2,494,126 Hoegberg Jan. '10, 1950 2,494,283 Cassaday etal 10, 19502,690,450 Gilbert -et :al -.Sept..28, 1954 2,761,806 Boyer -'Sept. 4,1956 2,766,170 Buntimetal. .-Oct.:9, 1956 2,793,224 Fancher May 2 1, 195.7

FOREIGN PATENTS 969,440 France Dec. 20, 1950 257,649 Switzerland May 2,1949 OTHER REFERENCES ;Germany,i-F 17452, 1V 'b/ 12 Mar 22, 1956.

1. AN S-(CHLOROPHENYL) O,O-DIALKYL PHOSPHORODITHIOATE HAVING THE FORMULA